Have You Had This Problem in PTC Sites?

First, you register for one site. Then you try to another for register.
Do you get this error that your IP has already been used to create an account you haven't really registered to that site? It's driving me crazy! I put up a discussion asking anyone if they are interested in trading for referrals, and it's when I found out I couldn't register for any site because of that error.
I feel like I made a fool of myself asking for referrals when I couldn't join in.

I haven't met this problem before. But if i had this problem, it won't be a problem. Because i can change my ip.
I'm not good at computer or internet. So I cann't help you solve this problem. Sorry!!! But you have to be more carefully next time~
Good luck!